Nanoscale materials, such as nanowires, nanotubes and nanofibers have gained more attention recently because of their unique electrical, optical and mechanical properties. Fabrication of oriented nanofibers on a planar surface and integration of these nanofibers with microfabricated structures such as electrodes of surface topography are required for application to molecular electronics. Randomly oriented nanofibers with diameters in the range of 50 to 500 nm have been fabricated using electrospinning technology and suggested for use in a wide range of applications such as high performance filters, drug delivery, scaffolds for tissue engineering, optical and electronic applications.
Vertically oriented tubes or metal needles, connected to syringe pumps have normally been used as electrospinning sources. In these systems, a droplet of solution is formed at the exit of a tube with diameter in the range of 300 um to 1 mm. The exit of the capillary tubing is normally directed downward to a counter electrode. A Taylor cone is established at the exit of the capillary tube by applying an electric field. A polymeric solution is extracted from the Taylor cone and electrospun toward the counter electrode surface. The distance between the exit of the capillary tubing and the counter electrode is approximately 5-25 cm with an applied electric field of 1000 V/cm to 3000 V/cm.
Straight nanofibers with diameters ranging from 100 to 300 nm have been fabricated by electrospinning on an edge of a sharpened rotational disc collector for possible application to molecular electronics. However, this approach does not permit fabricating of nanofibers on a planar surface. Therefore, it is difficult if not impossible to integrate nanofibers with microfabricated structures for such applications.